1. Field of the Invention
The present invention relates generally to environmental testing and, more particularly, to fixtures used in vibration testing.
2. Description of the Prior Art
Rectilinear vibration testing of devices to assure operation in their intended environment is a well established industrial practice. In performing such vibration testing, generally a device is secured to a fixture that is mechanically coupled to a source of rectilinear vibration, e.g. a pneumatically, electro-magnetically or hydraulically energized shaker driver. Recently, however, manufacturers have become concerned that rotational vibration and/or shock, as contrasted with rectilinear vibration and/or shock, may cause certain types of device failures, particularly for digital computer disk drives.
Presently, it appears that there exist several different commercial systems for applying a rotational shock to a device under test. One type of rotational shock system employs a spring-loaded plunger which, upon being released, strikes a pivoted plate to which is secured the device undergoing test. An alternative type of rotational shock system employs a plate that pivots about a horizontal axis to which is secured the device undergoing test. When released, the plate rotates downward until hitting a mechanical stop. The advantages of such rotational shock testing devices are that they are relatively simple to design, and they are relatively inexpensive. However, these different types of rotational shock testing devices have several disadvantages. First, it is difficult to control the strength of the applied shock, and therefore the systems exhibit poor repeatability. Second, the systems are capable of applying only a single, relatively weak shock having a duration that is difficult to adjust or control. Lastly, these systems are incapable of applying rotary vibration to a device undergoing test.